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Ch 312
Practice Exam #1
Name_____________________________________
(100 pts) You must show all work and follow significant figure conventions. Answers that do not
show work receive zero credit.
1. Matching (8 pts). Only one answer for each possible.
(a) _____ 10-15
(b) _____ 106
(c) _____ micro
(d) _____ milli
(e) _____ strong acid
(f) _____ weak acid
1. mega
2. nano
3. milli
4. femto
5. 106
6. 10-3
7. 10-6
8. 10-12
9. KOH
10. HClO4
11. NH3
12. HNO2
(g) _____ strong base
(h) _____ weak base
2. Basic Statistics (10 pts). Calculate the average, standard deviation, and the 95% confidence
level of the mean for the following data set (N=6) using the attached table of Student t-values:
5.74, 5.73, 5.84, 5.75, 5.55, 5.73.
3. Propagation of Errors (10 pts). In a percent purity KHP calculation, a student uses a mass
of 0.5472 ± 0.0015-g of pure KHP obtained from a 1.1075 ± 0.0034-g impure sample. Using
propagation of errors, what is the uncertainty in the percent purity?
4. Gravimetric Analysis (10 pts). A sample containing nickel was treated with
dimethylglyoxime (DMG), resulting in the precipitation of bis(dimethylglyoximate)
nickel(II). If the sample had a mass of 1.247-g and 3.761-g of precipitate was produced, find
the percent purity of nickel in the sample. Molecular weights (or formula mass, FM) are
given in the figure.
5. (4 pts) (a) Define relative supersaturation
(6 pts) (b) List three techniques used in a gravimetric analysis to increase particle size, and
explain them in terms of relative supersaturation.
i.
ii.
iii.
6. KHP Titrations (10 pts). A sample of KHP (MW = 204.223) weighing 1.017-g required
41.67-mL of a 0.09759 M NaOH solution for titration to the phenolphthalein endpoint.
Calculate the % purity of the KHP sample.
7. Buffers (10 pts). Find the pH of a solution prepared by dissolving 1.25-g of glycine amide
hydrochloride (BH+) plus 0.95-g of glycine amide (B) in 0.100L of H2O.
8. Solubility Equilibria (10 pts) - Common Ion Problem. The mercury(I) ion (Hg22+, also
called mercurous ion) is a diatomic ion with a total charge of +2. Mercury(I) iodate (MW =
750.99) dissociates into three ions:
Hg2(IO3)2(s) = Hg22+(aq) + 2 IO3-(aq)
Ksp = 1.3 X 10-18
(a) What is the solubility of Hg2(IO3)2 in pure water?
(b) What is the solubility of Hg2(IO3)2 in 0.010 M NaIO3?
(c) Explain the difference in (a) and (b) based on equilibrium concepts.
9. Activity (10 pts). Using activities and the attached table of activity coefficients, what is the
concentration of Ba2+ in a solution saturated with BaSO4 in (a) pure H2O, (b) 0.10 M KCl